Giant ragweed is just as bad for allergies as its common form

Garden Q&A

  • Autumn fern combines well with other shade-loving perennials.
Autumn fern combines well with other shade-loving perennials. (Courtesy of Debbie Ricigliano,…)
September 17, 2014|By Ellen Nibali | For The Baltimore Sun

A plant shot up about 6 feet in our yard recently. I never saw flowers, but the seeds remind me of ragweed. The leaf is not lacy like ragweed, though. It looks more like a stork footprint. What am I dealing with?

There is a bumper crop of ragweed this year, and you have a species known as giant ragweed (Ambrosia trifida), as opposed to common ragweed (Ambrosia artemissiifolia). Unfortunately, giant ragweed pollen causes highly allergic reactions, just like the more familiar species. Pull it immediately and bag it. It is an annual, and you don't want any seeds around to make life miserable next year.

How can I tell when a tree is hazardous? My oak tree has 3-foot-deep holes in the trunk, which hold water. Will this rot and kill the tree eventually? Should I have it cut down now?

Our online fact sheet, "How Do You Decide When to Remove a Tree?" can help you determine when a tree is a hazard and warrants removal. In your case, arrange for an evaluation by an arborist certified by the International Society of Arboriculture. Find a certified arborist at treesaregood.org. Evaluations are usually free.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to its website at extension.umd.edu/hgic.

Plant of the week

Autumn fern

Dryopteris erythrosora

There is no denying that a blanket of ferns in a woodland garden is a beautiful sight. Autumn fern provides an extra ornamental value. Early in spring, new copper-red fronds, which are very autumnal in color, emerge from the center of the plant. Mature fronds are a deep, shiny green. It grows to about 1-2 feet tall with a similar spread and can serve as a groundcover. Native to Japan, China and Taiwan, it combines well with other shade-loving perennials. As with most ferns, it is deer-resistant and has few disease or insect problems. Plant in partial shade and in moist, well-drained soil that has been amended with organic matter. They are drought-tolerant once established.

—Debbie Ricigliano

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